The invention relates to a fuel injection system of an internal combustion engine, and an internal combustion engine having such a fuel injection system.
In gasoline engines with direct fuel injection, the aim is to achieve the best possible distribution of the fuel in the combustion chamber and efficient, low-emission combustion of the fuel-air mixture in a so-called homogeneous operation of the internal combustion engine by means of the injection nozzles. For this purpose, in conventional fuel injection systems, injectors in the form of injection nozzles are usually used which open inwardly and generate a conical spray. Such injection nozzles customarily have five to seven injection orifices. To achieve good atomization of the fuel, the fuel may be injected into the combustion chamber with a fuel pressure of up to 20 MPa by way of the injection nozzle. However, wetting of the walls of the combustion chamber and the surfaces of the cylinder head and piston of the internal combustion engine, but also of the intake valves, with liquid fuel may result in undesirable increased pollutant emissions of the internal combustion engine, and therefore should be avoided to the greatest extent possible.
To avoid such undesirable wetting, it is important to control the interaction of the injected fuel spray with the internal flow of the air mass which is introduced into the cylinder. For example, internal combustion engines which are supercharged by means of an exhaust gas turbocharger often have a higher air mass motion in the form of a so-called “tumble flow,” thus increasing the influence of the distribution of the injected fuel. For internal combustion engines having a centered arrangement of the injection nozzle on the cylinder, the air mass motion guides the injected fuel to an exhaust side of the combustion chamber, as the result of which increased fuel concentrations may develop at that location, and undesirable wetting of the walls of the combustion chamber by fuel may occur.
DE 10 2009 046 001 A1 discloses a fuel injection system of an internal combustion engine having a combustion chamber with at least one intake valve on an intake side and with at least one exhaust valve on an exhaust side and with a central injection nozzle for injecting fuel into the combustion chamber. The injection nozzle has six injection orifices, a first partial quantity of fuel being injectable at the intake side by means of two first injection orifices and a second partial quantity of fuel being injectable at the exhaust side by means of four second injection orifices. Flow channels to the injection orifices have a respectively different design, so that the flow channels of the two first injection orifices have a higher flow resistance than the flow channels of the four second injection orifices. Contact of the cylinder walls with fuel may thus be reduced due to a shortened length of the injection jets of the two first injection orifices. However, contact of the cylinder walls with fuel by the injection jets of the four second injection orifices cannot be excluded.
DE 198 04 463 A1 describes a fuel injection system for gasoline engines, having an injection nozzle which injects fuel into a combustion chamber that is formed by a piston-cylinder structure. The combustion chamber has a spark plug which protrudes into the combustion chamber. The injection nozzle is situated in the central area of the combustion chamber, and is provided with at least one row of injection orifices which are distributed over the periphery of the injection nozzle, so that, by means of a targeted injection of fuel through the injection orifices, a spray-guided combustion process may be achieved by forming a mixture cloud. According to this combustion process, at least one fuel jet is generated, which for the ignition is directed at least approximately in the direction of the spark plug and controlled in such a way that only vaporized fuel is present in the area of contact with the spark plug. Together with additional fuel jets, at least one approximately closed and/or cohesive mixture cloud is formed, wherein no significant contact of the other jets with the piston or the cylinder wall of the internal combustion engine occurs.
It is the principal object of the present invention to provide an improved design for a fuel injection system in which the above-mentioned disadvantages are eliminated or at least reduced.